The present invention relates to an apparatus and method for separating and aerating a material stack formed of sheets, such as a stack of paper or the like.
A device and a method for separating and aerating a stack of material formed of sheets, such as a stack of paper, is known from DE 10 2004 003 455 A1. The device has a clamping device arranged in the transport path of the material stack, which is referred to as a “stack” for short in the following for the sake of simplicity. The clamping device has a pair of rollers with an upper and a lower rotating roller. Another component of the device is also a mechanism for adjustment of the rollers with respect to each other, in order to bring them into active connection with the stack for forming a clamping area of the stack between the two rollers. The device also has a stack support or board for horizontally holding the stack, as well as a member for guiding the stack in the area between the open roller pair, and for guiding the stack clamped between the rollers. In this device, the stack lying on the board is gripped by tongs, and then pulled with a horizontal movement component, whereby the clamping device acts on the pulled stack.
In such prior art devices, the rollers are arranged in exact vertical alignment, or on top of each other. In this way, the connecting planes between the two bearing axles of the rollers are arranged vertically. Between the clamping device designed in this way and the board for holding the stack, another rotating roller is arranged that has a rotary axle parallel to the rotary axles of the rollers of the clamping device. This third roller has the function of an intake roller, in front of which the stack that is guided away from the board, and is held by the tongs in the area of its front end and deflected diagonally downward on a significantly lower level than the upper edge of the additional roller between the two rollers of the clamping device. The third roller thus also has the function of a bending roller. Because of that, the stack has a wavy shape between the bending roller and the clamping device. The two rollers of the clamping device turn in opposite rotational directions while the stack is guided by the tongs, and support the sliding process of the stack, because of the double deflection. When the tongs are pulled forward, the sheets, especially the lower sheets, of the stack hang downward between the tongs and the clamping device. This described separating process makes possible the entry of air between the individual sheets. This separating process can be supported or enhanced by air nozzles arranged to direct air laterally into the stack.
Such prior art devices are very complicated in construction because of the need to provide the other roller and the large vertical traversing path, at least of the upper roller of the clamping device, in order to reach the clamping position. Besides this, the tongs are not driven only horizontally, but also vertically to a considerable extent. In sum, the device requires a complicated design because of the geometric specifications described. Also, the process sequence is complex because of the two-fold deflection of the stack in the area of the clamping device and the named other roller.
DE 26 41 214 C3 discloses a device for loosening a stack of sheets, in which the stack is moved between a clamping device that has rollers arranged on top of each other, whereby the connecting plane of the bearing axles of the rollers is arranged vertically. A wide roller is arranged on the bottom, and on top, the driven roller has a ring zone in its center offset to a smaller diameter. The lower roller consists, at least in the area of the outer shroud, of a compressible material, such as rubber elastic. While the stack runs through the roller pair, the lower roller is deformed elastically, with the formation of an indentation, and the stack is pulled around the upper roller at a specific angle. Because of this motion, there is a shift of the sheets lying on the upper side of the stack with respect to the sheets lying on the underside of the stack.
DE 32 19 693 A1 discloses a device and a method for separating and aerating a stack of material formed of sheets. A rotating lower belt and a rotating upper belt are provided, wherein the circumferential speed of the lower belt is slightly higher than the circumferential speed of the upper belt. The stack to be separated is supported on a horizontally arranged upper section of the lower belt, and guided in the direction of the lower section of the upper belt to where the belt sections of the upper and lower belts run parallel to each other and are at a distance that is matched with the thickness of the stack and diagonally downward with respect to the horizontal. Two rollers are arranged where the stack runs into the belt sections, and are contacted on the top and the bottom, whereby a lower roller is pressed from below against the upper section of the lower belt, and an upper roller is pressed from above against the lower section of the upper belt. The stack is guided between the belt sections of the two belts, which are arranged so they are angled or tilted. Because of the speed difference between the two belts, the lower sheets are pulled away faster than the upper sheets of the stack. Because the stack bends over the lower roller in the intake area of the stack, there is a certain separating of the partial stack due to the guiding of the sheets of the stack at different speeds. The separating continues along the belt sections of the upper and lower belts. The two rollers in the intake area of the stack are arranged in such a way that the connecting plane of the two bearing axles of the rollers is arranged at an angle with respect to the horizontal and the vertical. This angle is perpendicular to the parallel guiding sections of the two belts. Consequently, this device is complicated, and is based on a special function principle, namely, that the contacting of the stack is by upper and lower belts, and the rollers do not come directly into contact with the stack. In addition, the supply and the removal of the stack occur on a flat board according to the deflection geometry of the lower belt, whereby in the intake area, the belt is horizontally oriented, and in the outlet area, it is tilted with respect to the horizontal between the two belts according to the slope of the belts.